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I have a server that responds in a weird way to ping:

$ ping hostname.com
PING hostname.com (<IP address>) 56(84) bytes of data.
From hostname.com (<IP address>) icmp_seq=1 Destination Host Unreachable
From hostname.com (<IP address>) icmp_seq=2 Destination Host Unreachable
From hostname.com (<IP address>) icmp_seq=3 Destination Host Unreachable
From hostname.com (<IP address>) icmp_seq=4 Destination Host Unreachable

I'm confused, as the messages come from the server that I want to ping, and at the same time it's saying Destination Host (itself) Unreachable. Pinging by IP address yields the same result. The server is online and operating normally. What could be the cause?

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Is the IP address that hostname.com is resolving to actually configured on the server or is it a NAT in the firewall? – Paul Ackerman Feb 13 '12 at 13:34
It's a NAT in the firewall. Why does it make a difference? Pinging by IP is the same. – phunehehe Feb 13 '12 at 16:07
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It makes a difference because if the IP was configured on the box, you would have a TCP/IP stack problem or faulty NIC. Since the IP is configured on the firewall it is most likely dropping it because most firewalls do not allow traffic to flow in and out of the same interface. – Paul Ackerman Feb 13 '12 at 19:55
@Paul It is indeed because of the firewall, which didn't allow IMCP. However, that doesn't explain the weird respond to ping (it's saying itself is not reachable). – phunehehe Feb 14 '12 at 3:53
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what about the message makes not sense? that is says host unreachable? It makes perfect sense,since technically it uses ICMP to determine reachability, and if you block ICMP it is unreachable via ICMP – Doon Jul 27 '12 at 20:39
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closed as not a real question by Adrian, Tom O'Connor, mdpc, John Gardeniers, Ward Jan 6 at 5:28

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1 Answer

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It could be a firewall.

Compare the output from ip route with iptables -L

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